Because of lower weight and cost, among other things, so-called compact flanges are often preferred to conventional pipe flanges. An example of a compact pipe flange consists of the so-called “SPO Compact Flange” from Vector International Ltd, South Glamorgan, Great Britain.
In contrast to conventional pipe flanges, in which there is equipment for individual pressure testing of the gaskets in each flange, it is not possible to carry out such pressure testing of the gaskets in a compact flange.
Pressure testing of the gaskets must therefore be carried out by pressurizing the whole plant or parts of the plant in which the compact flanges are included, before the plant is put into service. Such pressure testing may include repeated flushing of the pipe because the pressure-testing medium must not be mixed with the medium that the system is going to handle.
From JP H07233887 A, a flange connection is known, consisting of two flange halves with centric bores and with annular gasket grooves in each flange half for receiving a gasket, the groove having an proximal side and a conical distal side. The associated gasket is formed to fit the grooves of the flanges and is further made with a plate-shaped portion extending inwards towards the bore of the flanges.
GB 952755 A discloses a flange connection with a groove with an outer conical surface and a gasket adapted thereto. In addition to a ring with an outer conical surface, the gasket also has plate portions extending both inside and outside of said ring. The inner seal may be formed of a second conical ring, for example. The gasket is further provided with a channel for use in leakage testing.
From U.S. Pat. No. 4,019,371 A, a device and method for testing flange gaskets consisting of a separate annular gasket and a plate-shaped gasket with a channel for leakage testing are known. The area that is pressurized for leakage testing is an annular volume outside the conical ring gasket.
WO03027561 A1 shows a gasket arrangement for flanges with the possibility of leakage testing between inner and outer gasket parts, but here the gasket is disc-shaped in its entirety.
WO9715814 A1 shows an arrangement for leakage testing flange gaskets, wherein the bore for supplying pressure is in one of the flange halves.